In many cases of abdominal aortic aneurysm (AAA), the diseased or weakened portion of the artery is near or up to the origins of the renal arteries. In these cases, it is difficult to get firm anchoring of the proximal end of an AAA stent graft. If the top stent of the stent graft cannot anchor to several millimeters of healthy tissue, there is a likelihood that there will be leakage around the top of the stent graft and/or migration of the stent graft out of the anchor area or “neck”, resulting in even more leakage and the failure of the stent graft to protect the aneurysm from arterial blood pressure.
In these cases, the common method for repair has been to add a short stent graft extension to the top of the main stent graft to extend the length of the top portion of the main stent graft back into the neck of the aneurysm, just below the renal arteries. The problem with this approach is that since the neck of the artery is short, these extension devices do not create a good reliable seal in the neck and are still subject to migration. Also, since there are so many different brands and sizes of stent grafts, it is difficult to provide a standard set of extension stent grafts that can be kept on hand, ready to use when the migration occurs. As soon as the leakage to the aneurysm resumes, the danger of rupture is immediate. There is little or no time to fabricate, sterilize and ship a custom manufactured product. In addition, if the extension stent graft is placed more proximal, up into the aorta, the extension stent graft will occlude one or both of the renal arteries, causing a failure of one or both kidneys. Since most of the stent graft patients are not good open surgery candidates, complete surgical replacement of the diseased abdominal aorta, the only other method of repair for a migrating stent graft, is not a good option.